I. Field of the Invention
The present invention relates to fuel pumps and, more particularly, to a high pressure roller vane stage of a motor vehicle fuel pump.
II. Description of Prior Art
An automobile generally will have an engine which derives its power from the internal combustion of fuel, such as gasoline. That same automobile will also have a tank in which fuel that is to be consumed by the engine is stored. The fuel stored in the tank is transferred to the engine by means of a fuel delivery system which commonly includes a fuel pump located in or around the tank and a fuel line leading from the fuel pump to the engine. One conventional fuel pump design uses an electric motor to drive to a high pressure roller vane stage to produce the necessary pumping action.
In such roller vane stages, low-pressure fuel from the tank is pulled into the roller vane stage through one or more inlet ports, and exhausted under high-pressure out one or more outlet ports into the fuel line. One particular roller vane stage includes a disk shaped inlet plate carrying the inlet port(s), a disk-shaped outlet plate carrying the outlet port(s) and a spacer position therebetween. The spacer has a central aperture or opening therethrough with an eccentric inner surface which defines a rotor space. A circular rotor element is rotatably mounted in the rotor space for rotation about the centroid or axis of the rotor. The rotor rotates within the spacer aperture so as to cooperate with the eccentric surface to pull fuel into the rotor space through the inlet port(s) in the inlet plate and to exhaust same out of the outlet port(s) in the outlet plate.
There are generally two different pumping actions taking place in such a roller vane stage design. In particular, the rotor has a plurality of lobes located circumferentially about its periphery such that each lobe opens radially outwardly toward the eccentric inner surface. A roller is associated with and movable within each lobe. The outer periphery and thus the lobe openings of the rotor pass closer to a smaller radius section of the eccentric surface and further from a larger radius section. The rotor spins to thereby produce pumping action. Consequently, as the rotor rotates about its axis within the rotor space, a respective lobe passes along changing radius sections of the eccentric inner surface of the spacer such that fuel is sucked into the lobe from a first or central inlet port as the lobe-roller combination rotates from a smaller radius section of the eccentric surface to a larger radius section, and fuel is exhausted therefrom out of a first or central outlet port as the roller is forced back into the lobe as the lobe-roller combination rotates from the larger radius section to the smaller radius section. Additionally or alternatively, a void in an area defined adjacent a segment of the rotor outer periphery located between two successive lobes increases in size as the rotor passes from the smaller radius section of the eccentric surface to the larger radius section to thereby suck fuel into the void through a second or outer inlet port. Similarly, the void shrinks as the rotor segment passes from the larger radius section to the smaller radius section to thereby exhaust the fuel out of a second or outer outlet port. Successive rotation of the lobes and the outer periphery provides for a continuous conversion of low-pressure fuel coming from the tank to high-pressure fuel supplied to the engine.
To rotate the rotor element, driver slots are usually punched or otherwise formed completely through the rotor element to either side of the rotational axis thereof. An electric motor is provided with driver tangs that drivingly engage the driver slots to spin the rotor upon actuation of the motor.
Fuel pumps equipped with these high pressure roller vane stages suffer from various problems such as high vibration, excessive noise, undesirable pressure pulse, and fluid cavitation. It is believed that the excessive noise and vibration cause many consumers to register complaints with automotive service departments. As the problems are believed to originate from the roller vane stage design itself, there is no readily available repair the service department can offer. Recognizing that the roller vane stage design itself may be the source of the problems, the service department may refused to replace the fuel pump. Even if the service department replaces the fuel pump, this action may not solve the problems, and depending on the condition of the replacement fuel pump, may accentuate the noise and vibration problems. In addition, fuel pumps based upon such roller vane stages also suffer from undesirable pressure loss and excessive fuel heating. It has been suggested that increasing the rotation speed of the rotor, or providing a larger pump stage, might relieve some of these problems. However, such remedial measures may increase the electrical demands on the motor and generate increased noise and vibration of the fuel delivery system. Consequently, such remedial measures are believed to be unacceptable solutions, and other more effective solutions are desired.